Abstract
The fresh mushroom off-flavour (FMOff) has been appearing in wines since the 2000s. Some C8 compounds such as 1-octen-3-one, 1-octen-3-ol, 1-hydroxyoctan-3-one, 3-octanol and others are involved in this specific off-flavour [1-3]. At the same time, glycosidic precursors of some FMOff compounds have been identified in musts contaminated by Crustomyces subabruptus [4], highlighting the role of aroma precursors in this specific taint. However, the fate of these volatile molecules and glycosidic fractions during fermentation is not well known. The aim of this work was to study the effects of alcoholic fermentation by Saccharomyces cerevisae (Levuline CHP® strain) on FMOff glycosidic precursors and volatile compounds present in healthy and contaminated Pinot noir musts, using Crustomyces subabruptus as fungal infection. The volatile compounds of FMOff and the glycosidic fractions of the initial musts and the resulting wines were analysed by GC-MS. The analysis of glycosidic precursors revealed for the first time the presence of 1-hydroxyoctan-3-one glycosides only in the contaminated musts.In addition, the Levuline CHP® strain was able to release a 1-hydroxyoctan-3-one glycosidic fraction during alcoholic fermentation. For the volatile FMOff compounds, the effect of fermentation was both compound and matrix dependent. Indeed, both 1-octen-3-one and 3-octanone showed fluctuating evolution depending on the initial matrix. The 3-octanol was systematically produced during alcoholic fermentation whatever the initial matrix with concentrations reaching up to 0.35 μg/L and 0.58 μg/L under healthy and contaminated conditions respectively. Finally, 1-hydroxyoctan-3-one reached an identical threshold concentration (around 150 μg/L) whatever the type of matrix and regardless of its initial level. Interestingly, this compound plays a dual role as substrate and product for the yeast highlighting a potential metabolic node in the FMOff biogenesis.